Herman Wallace, a terminally ill Louisiana inmate who served more than 40 years in solitary confinement, was released from prison Tuesday night, hours after a federal judge vacated his murder conviction and sentence, an attorney told CNN.

An employee at a prison where Wallace was incarcerated confirmed the release but would not give her full name. CNN left a message Tuesday night with a spokeswoman for the state Department of Public Safety and Corrections.

State officials had been threatened with contempt if they did not release Wallace immediately.

Wallace, who has liver cancer, is one of the "Angola 3" -- three inmates who claim they tried to point out injustices at the Louisiana State Penitentiary in Angola during the late 1960s and 1970s.

Wallace's sisters, nieces and nephews want him moved to hospice care in New Orleans, said one of his attorneys. The freed inmate left Hunt Correctional Center by ambulance, according to his lawyers.

"He has claimed there was an unfair trial for 41 years and finally we have that ruling," attorney Nick Trenticosta told CNN on Tuesday night. "For him to pass on from this world with friends and family at his side is extremely important."

The release came hours after U.S. District Chief Judge Brian A. Jackson in Baton Rouge said that women were systematically excluded from the grand jury that indicted Wallace in the 1972 slaying of a guard at Louisiana State Penitentiary.

Jackson declined to address Wallace's other claims, including an allegation that the state knowingly used false testimony and withheld exculpatory evidence at trial.

East Baton Rouge District Attorney Hillar Moore's office subsequently filed an appeal with the Fifth Circuit U.S. Court of Appeals and asked that Wallace not be immediately released.

But, in a strongly worded order, Jackson later Tuesday repeated his demand that Wallace be freed immediately, saying the state has failed to show Wallace would be a flight risk or public danger if released. He threatened them with a contempt judgment.

The judge ruled that prosecutors have 30 days to notify Wallace, 71, whether they intend to seek a new indictment in the case. CNN tried to reach Moore's office on Tuesday night, but was unsuccessful.

Wallace's legal team lauded the release of their client.

"Tonight, Herman Wallace has left the walls of Louisiana prisons and will be able to receive the medical care that his advanced liver cancer requires," they said in a statement. "It took the order of a federal judge to address the clear constitutional violations present in Mr. Wallace's 1974 trial and grant him relief. The state of Louisiana has had many opportunities to address this injustice and has repeatedly and utterly failed to do so."

Prison a "cauldron of brutality"

Wallace was in solitary confinement at Louisiana State Penitentiary until 2009, when he was moved to Hunt Correctional Center, where he remained in solitary until his diagnosis, according to Trenticosta.

Trenticosta said Wallace and another inmate at the Angola prison tried "to stop the guard brutality as much as the inmate brutality."

Inmates often were in control of the Angola prison and young men were taken in as sexual slaves by fellow inmates, Trenticosta added. "It was a cauldron of brutality."

Albert Woodfox and Wallace were convicted in the 1972 killing of Angola guard Brent Miller; a third inmate, Robert King, also known as Robert K. Wilkerson, also protested prison conditions. Together, they were known as the "Angola 3."

Woodfox and Wallace claimed they were targeted because of their activism as Black Panthers.

Wallace, who was serving an armed robbery sentence at the time of Miller's death, and Woodfox "were threatening the status quo," Trenticosta said.

King was transferred to Angola just weeks after the guard was killed. Even so, he was investigated as a possible "conspirator" and put into solitary confinement alongside Wallace and Woodfox, according to the documentary "In the Land of the Free." He was never convicted in connection with Miller's death.

King was convicted in 1973 of killing a fellow inmate. His conviction was overturned in 2001, and he was freed.

Diagnosed with cancer this summer

Wallace proclaimed his innocence in Miller's death in appeals.

"Mr. Wallace has fought his unconstitutional conviction for decades and is supported by four alibi witnesses who place him in another part of the prison when the tragic murder occurred," his lawyers said Tuesday.

According to his lawyers, Wallace -- after losing between 40 and 50 pounds -- was found this summer to have terminal liver cancer.

Chemotherapy treatment has not been effective and was suspended, according to Trenticosta, one of the attorneys for Wallace and Woodfox. He said the cancer should have been treated much earlier.

Wallace and Woodfox, who remains in prison with appeals pending in his case, "endured very restrictive conditions, including periods of 23-hour cell confinement," according to Amnesty International USA.

"Tragically, this step toward justice has come as Herman is dying from cancer with only days or hours left to live. No ruling can erase the cruel, inhuman and degrading prison conditions he endured for more than 41 years," Amnesty said Tuesday.

Trenticosta said he last saw Wallace a few weeks ago.

"There is no anger with Mr. Wallace," the lawyer said. "He is the strongest person I have had the great opportunity to represent. He is about positive thinking."